Last week it was the G8 environment ministers; this week it's a UN summit in Rome on the food crisis; next week it's finance ministers ahead of the G8 summit proper in Japan next month: all producing little more than hot air to add to the greenhouse gases threatening our planet

Fresh reports every day tell of glaciers melting, thinning polar ice triggering prospects of a new colonial scramble for the riches under the Arctic ice cap, dangers to the natural habitat of polar bears, worries about rising water levels inundating low-lying countries from Kiribati to Bangladesh, pieces of a trillion plastic bags that are discarded every year being fed mistakenly by albatrosses to their chicks on Midway Island in the remote Pacific Ocean, and soaring oil prices sending lorry drivers and fishermen across Europe to set up blockades.

With this background environment ministers from the G8 industrialised nations and leading developing countries, such as Brazil, China, India, Indonesia, Mexico and South Africa, together with their leading scientists and bureaucrats, met in Kobe, Japan, late last month to do something about the most pressing environmental issues facing this fragile planet Earth.

But three days of deliberations produced just another few million dollars of hot air. They agreed to try to agree to halve emissions of gases blamed for global warming by 2050 - which is almost two generations away - and called on the rich countries - which is them - to lead the way. Just to show that they have their eye on hot-button issues they also declared that reducing the use of disposable plastic bags and other consumer products is a good idea.

Ichiro Kamoshita, Japan's environment minister, who chaired the meeting, brushed aside any worries about the lack of a formal agreement, claiming that "the purpose of the G8 environment ministers' summit is not to negotiate agreements; the purpose is to provide a forum for discussion".

Devotees of the fine print of international diplomacy said that Kobe represented a significant step forward from last year's decision in Heiligendamm in Germany to "seriously consider" slashing output of greenhouse gases. Kobe now has its own special line in the index of international negotiations as "the Kobe Initiative".

It should be named "the Kobe Pious Wish". Indeed, how could anyone dream of reaching a real agreement while George W. Bush is in the White House? Scott Fulton of the United States Environmental Protection Agency said that the purpose of Kobe was to avoid "delicate subjects" such as mid-term emissions-reduction targets. How could it be otherwise when the US has rejected the Kyoto Protocol, which requires greenhouse gas cuts of a mere 5.2 per cent from 1990 levels by 2012.

Washington does its defiant diplomatic dance insisting that it will not cooperate until the newcomers to the big table moderate their fuel consumption. China and India, promise in advance not to drink too much. The newcomers respond by asking why they must restrict their growth when the already industrialised countries have despoiled the world's resources and polluted the atmosphere for years.

Even when George W. Bush vacates the White House, there are few reasons to be optimistic that a new US president, whatever the political colour, will change American attitudes. There is no evidence of any global vision from any of the US presidential contenders or any realisation that 300 million Americans share this planet with six billion other human beings.

Global warming itself is becoming a fervently fought issue that could turn into a latter-day religious war. Most scientists accept the overwhelming evidence that global warming poses a major threat to the world. But there are still small groups of non-believers, with powerful political and business backing, who demand more evidence or more time to prove dire fears.

Even among the believers there are deep divisions: some, such as Al Gore and Nicholas Stern, argue for strict action now to save the Earth for future generations; others claim that the prices Gore and Stern would impose on this generation are too high. One sect wants to pour resources into the development of new species of genetically modified trees, which will gobble up the harmful gases and thus remove the problem. Other sub-sects argue that scientists have always solved problems in the past, so there is no need to worry. Yet others argue that global warming has stolen the limelight, and that other issues such as environmental degradation, nuclear proliferation, global hunger and social injustice are more serious and immediate dangers to the planet.

So the hot air of greenhouse gases and the hot air of politicians talking continue virtually unabated.

Yes, it can be a complicated issue. Just to take the vexed question of plastic bags. American supermarkets have been offering "paper or plastic", but paper may be more polluting than plastic. Paper bags generate 70 per cent more air pollution and 50 times more water pollutants than plastic bags, and take up more landfill space, with 2,000 plastic bags weighing just 30lbs or 14kg, whereas 2,000 paper bags weigh 280lbs. On the other hand, the trees that produce paper bags are a renewable resource, while plastic bags are made from polyethylene, produced from non-renewable oil and natural gas.

Yet the lesson surely is that there is now an urgent need to modify and soften the damaging footprint of human beings on this Earth. The issues are interlocked, and arguing over which should be tackled first encourages inaction and exacerbates the problems. The rising world population has seen the available land per human fall from eight hectares in 1900 to about two today. The cutting down of forests, pollution of water sources, demands for higher standards of living, more energy consumption without paying the full price, are all killing the planet. In the last few weeks, rising energy prices have given new power to Brazil's soya bean ranchers to plunder the Amazon rainforest to grow their crops.

Americans are complaining about the high price of fuel for their gas-guzzling cars as petrol reaches US$4 a gallon. But US prices are relatively cheap by world standards and only half those of Europe. China and India also have lots to learn about responsible economic management. India pays out the equivalent of more than £10 billion a year in subsidies to keep petrol and kerosene prices below market rates, and China's prices are lower still.

It is surely time for the G8 leaders to take some simple steps that might pave the way for more substantial measures. First, admit China and India as full members to the group, so that they are part of the solution not an extension of the problem. Next, commit to minimum fuel-efficiency measures for vehicles, petrol prices that reflect the market - say, set a minimum $5 a gallon - and shared moves to promote energy efficiency. Learn from what Japan did in the first oil shock of the 1970s when energy efficiency doubled in a few years in terms of the fuel required to produce a unit of energy.

The markets and smart financial speculators are already making a mockery of the politicians. Prices of oil have doubled since May 2007 from US$65 a barrel to $130 and $200 a barrel oil is no longer fantasy but round the corner. But global demand has risen by just 2 per cent.

Speculators have also been busy driving up prices of food and other commodities, adding to the existing squeeze on global supplies, thanks to potentially devastating combinations of drought and disaster, diversion of food crops to use for fuel, growing demand for greater and better food in fast-growing developing countries along with continuing over-consumption in the meat-eating West. All these have helped push food prices up by 50 per cent and threaten a billion of the world's poorest people with starvation because they cannot afford food.

The United Nations called a summit in Rome this week, but the unexpected arrivals of Robert Mugabe, taking a few days off to enjoy the high life away from his starving people in Zimbabwe, and Mahmoud Ahmadinejad of Iran threatened to turn the three-day meeting from an important discussion of the issues into political theatre of the absurd.

Common action may stick in the American craw. But the alternative is the law of the jungle. Who will win? China and India are better placed than the profligate US, used to a high-energy-consuming economy that has run up huge debts on its national accounts. China has huge foreign- exchange reserves and has quietly been wooing friends worldwide to assure its supplies of oil and other key commodities.

But we all - American, Asian, European or African - have to learn that we share this fragile home and we will all suffer from its damage, just as the albatross chicks on remote Midway are paying for the plastic waste of the West.